Electric heat lamp and electric devices



Dec. 17, 1968 Q N v 3,417,230

ELECTRIC HEAT LAMP AND ELECTRIC DEVICES Filed Dec. 15, 1966 Fig. 1

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United States Patent 3,417,230 ELECTRIC HEAT LAMP AND ELECTRIC DEVICES Roger C. Millikan, Schenectady, N.Y., assignor to General Electric Company, a corporation of New York Filed Dec. 15, 1966, Ser. No. 601,929 4 Claims. (Cl. 219-553) This application discloses improved electric heat lamps and electric heater devices wherein heat and light are emitted from a coiled incandescable refractory filament which is completely sealed in intimate contact to the exclusion of all ambient air or gaseous atmosphere within a rod of a light-transmissive, vitreous, high softening point quartz or quartz-like substance having a low thermal coeificient of expansion, and which may be deformed by the application of appropriate heat and mechanical stress into any desired shape or configuration, as for example, a circular coil, a helical spiral, or a planar spiral to form heat lamps and heat elements, as desired.

This application is related to my concurrently filed copending application, Serial No. 601,930 and the concurrently filed copending application of Millikan and Osburg, Serial No. 601,927, both of which are assigned to the present assignee.

Heat lamps of the prior art are generally composed of heavy-duty refractory, incandescable filaments sealed by conventional lamp techniques within an evacuable envelope which may be operated in vacuo or in a low pressure of an appropriate buffer gas. Suitable filters may be provided, either within the gaseous atmosphere in the envelope or upon the lens of the lamp to filter out short wavelength radiation so as to provide heat which may contain little or no visible radiation. While these lamps are highly eflicient and useful sources of heat, they are exceedingly fragile due to the evacuable envelope and are quite expensive in that the envelope must be of very rugged construction in order to withstand the handling to which heat lamps are subjected. Similarly, because the filaments thereof are operated at exceedingly high power in order to obtain the maximum heat therefrom, the lamps tend to have a short lifetime due to the evaporation, sputtering, or otherwise removal of material from the tungsten filament with the consequent deterioration thereof.

Accordingly, it is an object of the present invention to provide heat lamps and heat elements which are constructed without the necessity of an evacuable envelope.

Another object of the present invention is to provide exceedingly rugged long-lived heat lamps and heat element devices wherein the heat emitting member is completely shielded from any deleterious atmosphere.

Yet another object of the present invention is to provide heat lamps and heater devices which may be fabricated in any desired shape, and the shape of which may be changed to suit the desired application.

Briefly stated, in accord with the present invention, I provide heat lamps and heater elements comprising a helical coil of tungsten or other refractory metal wire having a very small cross-section which is completely and heremetically imbedded within a rod of a suitable light-transmissive, vitreous, high temperature-resistant material, as for example, quartz or any of the predominantly silica, quartz-like materials, to provide an elongated structure which may be fashioned into any desired shape to form a heat lamp as for example, into a circular shape. In accord with another embodiment of the present invention the same rod-like structure may be deformed into a re-entrant U-shaped configuration and used as an immersion heater. In accord with another embodiment of the invention the same rod-shaped light and heat producing element may be wound into a planar helical spiral to form a flat heater element suitable for use as a heater element in an electric range.

The novel features believed characteristic of the present invention are set forth in the appended claims. The invention itself, together with further objects and advantages thereof, may best be understood by reference to the following detailed description taken in connection with the appended drawing in which:

FIGURE 1 is a view in vertical cross-section, with parts broken away, of a heat lamp element constructed in accord with the present invention;

FIGURE 2 is an alternative embodiment of the device of FIGURE 1 wherein the heater element is formed into a circular shape;

FIGURE 3 is another alternative embodiment of the present invention wherein the heater element is bent into a re-entrant U-shaped type suitable as an immersion heater; and

FIGURE 4 is yet another alternative embodiment of the invention wherein the heater element is wound in a planar spiral to form a range-top type heater element.

As mentioned hereinbefore, conventional heat lamps are made along the lines of a conventional lamp in that an incandescable filament, generally of heavy duty construction, is suspended within an evacuated or low pressure glass envelope which has all of the disadvantages of an evacuated envelope with a fragile refractory filament suspended therein. Additionally, due to the high temperature and heavy loading of the filaments thereof life-times of such devices are exceedingly short due to sputtering, evaporation and other removals of metal from the incandescable filament thereof. In my copending application, Serial No. 601,930 and the copending application of R. C. Millikan and L. A. Osburg, Serial No. 601,927, both filed concurrently herewith and assigned to the present assignee, the entire disclosures of which are incorporated hereinto by reference thereto, I have disclosed and claimed improved structures and methods for the construction of incandescent lamps in which an incandescable refractory filament having a helical configuration is directly and hermetically sealed through a high temperature vitreous, light-transmissive envelope which has a low thermal coefficient of expansion, and improved structures for insuring that the small diameter incandescable filament is adequately protected against deterioration, oxidation, and destruction by high temperature operation in ambient air upon the emergence thereof from the envelope wall. In accord with the present invention I am able to adapt the fundamental concepts disclosed and claimed in the aforementioned copending applications and modify the structure in order to provide improved heat lamps and heat element devices wherein the incandescable filament is completely enclosed and hermetically sealed within and to a solid light-transmissive, high temperature vitreous material in an elongated tubular element which may be shaped to any desired configuration.

Thus, while the incandescent lamps of my aforementioned copending application and the copending application of Millikan and Os'burg provide for an evacuable space within which an incandescent filament is located, either in vacuo or in a butter gas, the heating elements and lamps of the present invention contemplate the complete enclosure of the incandescent filament of refractory metal within and in intimate contact with the high temperature, vitreous light-transmissive material of which the body of the element is constructed.

The primary objective of the present invention is the provision of a light emitting heat lamp capable of operation at temperatures of the order of 1000 C. or higher.

To this end I use refractory metal filaments completely sealed within quartz-like, high temperature-resistant rods. I am aware that in the prior art, others have provided various heater elements for windshield defrosting, immersion heating and other low temperature applications by the sealing of low temperature melting point resistance alloys such as nichrome and chromel in Pyrex glass and the like bodies. Due to the reasonably close match in thermal coefficient of expansion of these bodies the problems that have heretofore prevented the construction of heat lamps and heating elements in accord with the present invention were not present. Additionally, since even Pyrex glass softens at approximately 500 C. to 600 C., such devices are only useful for low temperature heating and, since a filament does not become heated to white or even red heat at that temperature, such devices are completely incapable of producing high temperature radiant energy. Such radiant heat may only be produced by raising the filament to temperatures using the refractory filaments used herein and the high silica quartz-like or higher temperature materials used herein. Prior to the inventions set forth in the aforementioned copending applications, it was not possible to make hermetic seals between such refractory metals and such quartz-like light-transmissive materials.

In FIGURE 1 of the drawing a vertical cross-sectional view of a schematically illustrated elemental form of heat lamp, in accord with the present invention, is illustrated. In FIGURE 1, a cylindrical rod 1 of a high temperature, light-transmissive, vitreous material, as for example, quartz (or any material which is predominantly silica, as for example Corning Vycor, and has the low temperature coefiicient of expansion and high temperature softening point which will be denominated herein as quartzlike characteristics, has a slight tapered portion 2 at either end thereof and a hollow aperture 3 therein, terminated in a cusp-shaped region 4 which terminates in a point 5 through which extends the end 6 of a helically coiled, refractory metal incandescable filament 7. Filament 7 may be any refractory metal having an atmospheric pressure melting point of in excess of 2500 C- and a room temperature resistivity of at least 4.5x l0 ohm-cm. such as tungsten, molybdenum or rhenium. In accord with the invention disclosed and claimed in the aforementioned Millikan and Osburg application, a metallic solidified mass 8 completely surrounds the extending end 6 of filament 7, making electrical contact thereto and rigidly mechanically supporting end 6 within cusp shaped end 4 of aperture 3. An electrically conductive lead and support member 10 is also imbedded within mass 8 of solidified metal and provides means for supplying a voltage to cause the incandescence of filament 7, to cause the production of the substantially black-body radiation thereof, which is primarily in the infrared region and which provides an excellent source of heat which render the device suitable as an element of a heat lamp.

In accord with the present invention filament 7 is constructed of a refractory metal having a very high melting point in excess of approximately 2500 C. and a relatively high electrical resistance. As is defined hereinbefore the material from which tubular section 1 is constructed is a quartz-like material having a very high resistance to deformation or melting upon heating and which mav conveniently withstand temperatures of 1200 to 1400 C. without any appreciable deterioration or softening thereof. Such material may, however, be controllably and de sirably softened so as to shape the same into any desired configuration. The resistance of the filament 7 and hence the length and coil diameter thereof are designed in accord with the voltage to be applied between electrical terminals 10 so that, when the voltage is applied under operating conditions, the temperature of the filament reaches a suitable operating temperature, as for example, approximately 1000" C. It is possible, however, to operate safely and conveniently at this temperature because the characteristic of the high temperature, vitreous, lighttransmissive envelope 1 is such as to withstand this temperature without any deleterious effect.

Conveniently the element of FIGURE 1 may be mounted by mechanically clam-ping the ends thereof within an appropriate reflector, parabolic, spherical, or otherwise, depending upon the particular design desired, and may be utilized to direct the radiation thereof, as is conventional with heat lamps, but without the necessity of enclosing the same with a hermetic seal to protect the filament thereof from deterioration by oxidation, since it is already sealed from atmospheric air and may operate continuously for many hours with no observable deterio ration whatsoever.

In FIGURE 2 of the drawing there is illustrated an alternative embodiment, wherein the tabulation 1 is formed in the shape of a circle and filament 7, conforming thereto, has the same juxtaposition therewithin, being fully enclosed therein and freelybending with the quartz or quartz-like material from which envelope 1 is fabricated. End members 9 and electrode leads '10 are essentially the same as in the device of FIGURE 1.

In FIGURE 3 of the drawing a tubular rod 1 of a quartz or quartz-like material having disposed therein an incandescable filament 7 of a high resistance, refractory material, as for example, tungsten, wound in the form of a helical coil is deformed by appropriate application of heat and mechanical stress into a U-shaped member having electrical leads 10 connected thereto which may suitably serve as an immersion heater for heating of liquids to any desired temperature. As with the heat lamps illustrated in FIGURES 1 and 2, the device may be operated at temperatures of approximately 1000 C. at the incandescable filament which, when in thermal'equilibrium with a liquid in which it is immersed, is useful to rapidly and effectively bring a liquid to a desired high temperature. Since quartz and quartz-like materials as described hereinbefore are highly non-reactive with reactive liquids, particularly as strong acids, bases and even molten metals, such an immersion heater is effective in many applications in which conventional immersion heaters having metallic or glass sheathing which is susceptible to chemical attack, may not be used. The general structure of the tubulation 1 prior to fabrication in the shape as illustrated in FIGURE 3 is substantially that as in FIGURE 1 of the drawing.

In FIGURE 4 of the drawing there is illustrated a planar spiral heater element fabricated from a high temperature quartz-like material, as for example, quartz, substantially as illustrated in FIGURE 1 of the drawing and containing therein an incandescable filament 7 terminating in electric leads 10. This device may be used, as for example, as an electric heater element for a range or hot plate. Conveniently, since in this application there is no advantage for the emission of light, a suitable pigment may be added to the material from which tubulation 1 is formed prior to fabrication of the tubulation and assembly thereinto to form the heater element, to cause the quartz-like material to have any desired color to match with any suitable decor in an electrical appliance into which it may be incorporated.

Devices in accord with the present invention may conveniently be fabricated in accord with the process set forth in my aforementioned copending application, Serial No. 601,930, with the exception that, rather than having a large internal diameter to the tubulation, the tubulation utilized need only have a single diameter bore which is substantially the diameter of aperture 3 in FIGURE 1 of the drawing. A suitable length of the tubulation is cut and a suitable length of hedically coiled, incandescable refractory filament material as for example, tungsten, having a Wire diameter not to exceed 0.004 and, for practical purposes having a minimal useful diameter of approximately 0.0005". Alternatively, a convenient coiled-coil filament as described in Fridrich Patent No. 2,883,571, for example, may be used to obtain greater power output per unit length. The filament is inserted into the tubulation and supported therein while the tubulation is heated by a convenient means, as for example, by a plurality of oxyhydrogen torches beginning at the center of the tubulation and working outwardly to the ends to prevent the entrapment of air or gas bubbles therein. The tubulation temperature is raised slowly so that the incandescable filament is also raised to a temperature of from 1750 to 2200 C. to cause out-gassing thereof and cleansing of the surface thereof, to make a clean and firm bond between the quartz or quartz-like tubulation as it collapses thereabout and fully encompasses the spiral of the incandescable filament. The entire length of the tubulation is treated as described with respect to the end portions of the tubulation of the incandescent lamp in my aforementioned copending application to cause the entire filament to be completely enclosed within the quartz or quartz-like material of the tubulation and, thereby, completely insulate and protect the filament from ambient atmosphere and to preclude any removal of metallic particles therefrom with the resultant deterioration of the filament. End caps of a solidified metal or alloy having a melting point of from approximately 600 C. to 1500 C. are then melted and solidified within ends 3 of tubulation 1, as is described in greater detail in the aforementioned copending Millikan and Osburg application.

One device in accord with the invention is a heat lamp radiator as illustrated in FIGURE 1. The tubular support member is a 3" long 0.250" OD quartz rod having a 005+" ID with a tungsten helical spiral with a 005-" outside diameter made of 0.002 wire. The filament is imbedded within and contacted by the quartz by heating for 3 minutes by a pair of oxy-hydrogen torches. End seal masses of approximately 1 gram each of nickel support the filament ends. Nickel wires are used for electrical contacts. The element is supported by an insulating shield at the focal point of a 6" diameter parabolic reflector to form a heat lamp.

While the invention has been disclosed herein with respect to certain embodiments thereof, many modifications and changes will readily occur to those skilled in the art. Accordingly, I intend by the appended claims to cover all such changes as fall within the true spirit and scope of the present invention.

What I claim as new and desire to secure by Letters Patents of the United States is:

1. An electric heat emitting device comprising:

(A) A support member of vitreous, light-transmissive material capable of withstanding temperatures of at least 1000 C. without softening;

(B) A coiled refractory metal wire incandescable filament hermetically sealed and fully imbedded within the volume of said support member and extending outward through the ends thereof;

(B1) The material of said support member being in intimate contact with said wire along the entire length thereof which is imbedded therein;

(C) A mass of metallic material moulded about the outwardly extending ends of said filament and making good electrical contact and a strong mechanical supporting contact thereto;

(D) Contact means in electrical contact with said metallic mass for supplying an operating voltage to said filament; and

(E) said support member being an elongated tubulation of high silica content quartz-like material and the filament being a refractory metal wire having a melting point in excess of 2500 C. and an electrical resistivity at room temperature at least as high as 4.5 10 ohm cm.

2. The device of claim 1 wherein the filament is made of a material selected from the group consisting of tungsten, molybdenum and rhenium and has a wire diameter of approximately 0.0005'-' to 0.004".

3. The device of claim 1 wherein the tubulation is of quartz and the filament is of tungsten.

4. The device of claim 1 wherein the tubulation is light-transmissive and adapted to be the principal element of a heat lamp.

References Cited UNITED STATES PATENTS 2,007,111 7/1935 Morgan 219-544 2,063,826 12/1936 Pender 338-329 X 2,604,572 7/1952 Hudson 219-536 2,606,989 8/1952 Gomersall 219-536 2,727,979 12/1955 Altosaar 219-319 2,795,683 6/1957 Teiger 219-473 2,800,565 7/1957 Gritfin et a1. 219-300 2,813,960 11/1957 Egle et al. 219-345 2,902,578 9/1959 Johnson et al. 219-245 2,902,581 9/1959 Stiebel 219-513 3,249,959 5/1966 Theckston 15-25006 FOREIGN PATENTS 362,469 7/ 1962 Switzerland.

BERNARD A. GILHEANY, Primary Examiner. VOLODYMYR Y. MAYEWSKY, Assistant Examiner.

US. or. X.R. 219-464, 544, 523; 2s0 219; 338-329, 263 

1. AN ELECTRIC HEAT EMITTING DEVICE COMRPISING: (A) A SUPPORT MEMBER OF VITREOUS, LIGHT-TRANSMISSIVE MATERIAL CAPABLE OF WITHSTANDING TEMPERATURES OF AT LEAST 1000*C. WITHOUT SOFTENING; (B) A COILED REFRACTORY METAL WIRE INCANDESCABLE FILAMENT HERMETICALLY SEALED AND FULLY IMBEDDED WITHIN THE VOLUME OF SIAD SUPPORT MEMBER AND EXTENDING OUTWARD THROUGH THE ENDS THEREOF; (B1) THE MATERIAL OF SAID SUPPORT MEMBER BEING IN INTIMATE CONTACT WITH SAID WIRE ALONG THE ENTIRE LENGHT THEREOF WHICH IS IMBEDDED THEREIN; (C) A MASS OF METALLIC MATERIAL MOULDED ABOUT THE OUTWARDLY EXTENDING ENDS OF SAID FILAMENT AND MAKING GOOD ELECTRICAL CONTACT AND A STRONG MECHANICAL SUPPORTING CONTACT THERETO; 